Cookies on the NHS website
We've put some small files called cookies on your device to make our site work.
We'd also like to use analytics cookies. These send information about how our site is used to services called Adobe Analytics, Hotjar and Google Analytics. We use this information to improve our site.
Let us know if this is OK. We'll use a cookie to save your choice. You can read more about our cookies before you choose.
I'm OK with analytics cookies Do not use analytics cookies
Search the NHS website
Search
My account
Health A-Z
Live Well
Mental health
Care and support
Pregnancy
Browse
More
Coronavirus (COVID-19)
Get the latest advice about COVID-19
Home Health A to Z
Irregular periods
Irregular periods aren't always a sign of a problem, but sometimes it's a good idea to see a doctor about them just in case.
What are irregular periods?
You have irregular periods if the length of your menstrual cycle (the gap between your periods starting) keeps changing.
Your periods may come early or late.
The average menstrual cycle lasts 28 days, although it's normal for it to be a bit shorter or longer than this.
After puberty, many women develop a regular cycle with a similar length of time between periods. But it's not uncommon for it to vary by a few days each time.
Causes of irregular periods
There are many possible causes of irregular periods. Sometimes they may just be normal for you.
Common causes include:
puberty – your periods might be irregular for the first year or two
the start of the menopause (usually between the ages of 45 and 55)
early pregnancy – take a pregnancy test to rule this out
some types of hormonal contraception – such as the contraceptive pill or intrauterine system (IUS)
extreme weight loss or weight gain, excessive exercise or stress
medical conditions – such as polycystic ovary syndrome (PCOS) or a problem with your thyroid
When to see a GP
You don't need to get medical advice if you have always had slightly irregular periods or you're still going through puberty.
But see a GP if:
your periods suddenly become irregular and you're under 45
you have periods more often than every 21 days or less often than every 35 days
your periods last longer than 7 days
there's a big difference (at least 20 days) between your shortest and longest menstrual cycle
you have irregular periods and you're struggling to get pregnant
There might not be anything wrong, but it's a good idea to get checked out to see what the cause might be.
You might be referred to a specialist called a gynaecologist if you need any tests or treatment.
Trying for a baby
It can be more difficult to get pregnant if you have irregular periods because you might not ovulate (release an egg) regularly.
It can help to have sex every 2 or 3 days throughout your cycle. You don't need to time sex around ovulation.
Read more about trying to get pregnant.
Sometimes hormone medicine or fertility treatment may be needed if you're struggling to get pregnant naturally.
More about periods and other period problems
Read more about:
periods and the menstrual cycle
heavy periods
stopped or missed periods
period pain
Video: menstrual cycle
This animation explains in detail how the menstrual cycle works.
Play Video
Media last reviewed: 21 October 2020
Media review due: 21 October 2023
Page last reviewed: 27 April 2021
Next review due: 27 April 2024
Support links
Home
Health A to Z
Live Well
Mental health
Care and support
Pregnancy
NHS services
Coronavirus (COVID-19)
NHS App
Find my NHS number
Your health records
About the NHS
Healthcare abroad
Contact us
Other NHS websites
Profile editor login
About us
Accessibility statement
Our policies
Cookies
© Crown copyright